Field of Invention
The present invention relates to the attachment of working implements to agricultural vehicles, and in particular to methods for the attachment which may be implemented where the vehicle is equipped with a mounting hitch or similar connector which hitch is movable relative to the vehicle, and further to an agricultural vehicle having such a hitch and a control system for at least partially automated control of the hitch.
Description of Related Art
An example of such a movable hitch is described in International Patent application WO 90/06240 and comprises a towing hook attached at one end of a towing bar, with the other end of the towing bar slideably mounted in a frame. The hitch frame is pivotably mounted to the chassis of a tractor and enables the towing hook to be raised or lowered by rotating the frame up or down about the pivoting mount. The towing hook is further movable towards and away from the vehicle chassis by operation of a hydraulic cylinder which controls the sliding movement of the towing bar within the frame. Further examples of such movable hitches are described in German Patent application DE 100 65 161 A1 and European Patent application EP 1 428 696 A1.
It will be understood that the form of connecting means will be determined by the configuration of implement that is to be coupled. For example, a rigid transverse beam with spaced connectors may be used for semi-mounted implements, such as certain configurations of plough, whereas a quick release hook or a ball hitch coupling may be used for towed implements such as sprayers or balers. The term “connection hitch” as used herein is intended to encompass all such arrangements.
One particular benefit of having a movable connection hitch arises in the connection or mounting of implements, whereby small adjustments in the relative position of tractor and implement to align for connection may be made by moving the hitch rather than the whole tractor.
A downside of having a movable connection hitch is in terms of managing axle loading. If an implement is mounted on the hitch at the furthest extent of its movement away from the vehicle rear axle, the extra leverage about the axis of the rear axle will lead to the front axle raising and hence require additional front-mounted weights to counterbalance the implement. If, on the other hand, the hitch is brought in to its closest position to the rear axle, there is a risk of the implement fouling the rear wheels, especially during turning.